What is PulseAudio:

PulseAudio Logo
PulseAudio is a sound system for POSIX OSes, meaning that it is a proxy for your sound applications. It allows you to do advanced operations on your sound data as it passes between your application and your hardware. Things like transferring the audio to a different machine, changing the sample format or channel count and mixing several sounds into one are easily achieved using a sound server.

It is an integral part of all relevant modern Linux distributions (Debian, Kali Linux etc.) and used in various mobile devices by multiple vendors.

Features

The main features includes:

  1. Per-application volume controls
  2. An extensible plugin architecture with support for loadable modules
  3. Compatibility with many popular audio applications
  4. Support for multiple audio sources and sinks
  5. Low-latency operation and latency measurement
  6. A zero-copy memory architecture for processor resource efficiency
  7. Ability to discover other computers using PulseAudio on the local network and play sound through their speakers directly
  8. Ability to change which output device an application plays sound through while the application is playing sound (without the application needing to support this, and indeed without even being aware that this happened)
  9. A command-line interface with scripting capabilities
  10. A sound daemon with command line reconfiguration capabilities
  11. Built-in sample conversion and resampling capabilities
  12. The ability to combine multiple sound cards into one
  13. The ability to synchronize multiple playback streams
  14. Bluetooth audio devices with dynamic detection
  15. The ability to enable system wide equalization

Related (ALSA)

ALSA provides a software mixer called dmix, which was developed prior to PulseAudio. This is available on almost all Linux distributions and is a simpler PCM audio mixing solution. It does not provide the advanced features (such as timer-based scheduling, and network audio) of PulseAudio. On the other hand, ALSA offers, when combined with corresponding sound cards and software, low latencies. There’s a different issue in Kali Linux where sound is muted at boot. You can follow some simple 2 line instructions to fix sound mute in Kali Linux on boot time.

The Warning Message during boot

My Kali throws me this warning:

[warn] PulseAudio configured for per-user sessions ... (warning).

Debian variants also throws similar warning during boot.

To fix this do

leafpad /etc/default/pulseaudio

Find this line:

PULSEAUDIO_SYSTEM_START=0

Replace 0 with 1

PULSEAUDIO_SYSTEM_START=1

Where,
0 = don’t start in system mode, 1 = start in system mode

reboot

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